Carburetor



July 2, 1957 OLSON CARBURETOR Filed Sept. 21,

INVENTOR. 5mm 0150 H/s ATTOHNIY CARBURETOR Elmer Olson, Rochester, N.Y., assignor to General Motors Corporation, Detroit, Mich, a corporationof Delaware Application September 21, 1954, Serial No. 457,344

4 Qlaims. (Cl. 261-41) This invention relates to a carburetor forsupplying a combustible mixture of fuel and air to an internalcombustion engine, particularly an engine for automotive use and isconcerned primarily with the specific construction of the fuel supplymeans in the carburetor.

It is generally the practice in carburetors at the present time tointroduce fuel, when the engine is idling, through an inlet or inletspositioned adjacent the throttle and fuel is supplied thereto through aconduit which is, at least in part, separate from the main fuel supplysystem. The main fuel inlet, to which fuel is supplied by anotherconduit, is not operative during idling, but when the engine isoperating under load and the throttle is moved toward open position atsome point in the throttle movement, the main fuel inlet becomeseffective. Also, at some point in the throttle movement the idling fuelinlet becomes ineffective, the amount of fuel supplied by the idlingfuel inlet decreasing as the throttle is moved toward open position,while the fuel supplied by the main inlet increases as the throttleopens.

During a part of the opening movement of the throttle, both main andidle fuel inlets are effective, but ultimately, the throttle reaches aposition where the supply of fuel from the idling system ceases entirelyand thereafter, as the throttle moves from this position until it iswide open, all of the fuel supplied to the carburetor comes from themain fuel inlet.

It has been found that during some engine operation with the throttlepartly open before the idling system ceases to function and when thetransfer from the idling fuel system to the main supply system iseffected, the flow of fuel, particularly from the main fuel inlet, issomewhat irregular and it is the primary object of the present inventionto overcome this difficulty and provide means for improving the functionof the main fuel supply system under the specific conditions referredto.

Further objects and advantages of the present invention will be aparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawings:

Figure l is vertical section through the entire carburetor taken on theline 1-1 of Figure 2;

Figure 2 is a plan view of the fuel chamber casting as seen from theline 22 of Figure 1;

Figure 3 is a fragmentary section on the line 3-3 of Figure 2; and

Figure 4 is a detail section on line 4-4 of Figure 3.

The carburetor shown in the drawings is a dual carburetor intendedprimarily for use on an eight-cylinder engine and in many respects itsconstruction is the same as carburetors which have been previouslydesigned. Therefore, much of the construction of the carburetor is notdescribed in any degree of detail.

As illustrated, the carburetor includes three separate castings 2, 4 and6 positioned above each other and separated by suitable gaskets. An airpassage 8 is formed 2,797,905 Fatented July 2, 1957 ice in casting 2 andthis passage supplies air to two mixing chambers 10 and 12 formed in thecasting 4 and separated by a partition wall 14 which is a part ofcasting 4. In these chambers a combustible mixture is formed which isconveyed to the intake manifold through two outlet passages 16 and 18,which are formed in the casting 6 and connect with passages formed inthe manifold. The casting 6 is supported directly on the manifold in theconventional manner.

The quantity of mixture which passes through passages 16 and 18 iscontrolled by throttles 20 and 22, respectively, both of which aresecured to a single manually operated throttle shaft 24 suitablyjournalled for rotation in the wall of casting 6 and operated by an arm26 secured in any desirable way to the right end of shaft 24 as seen inFigure l. The arm 26 is adapted to be connected by a suitable operatingconnection (not shown) to the conventional foot operated acceleratorpedal. The operating mechanism for the throttle shaft is neither shownnor described in detail herein as the construction of this mechanism isa matter entirely immaterial so far as the present invention isconcerned.

Air enters the passage 8 through an opening 28 and the admission of airto such passage is controlled by a choke valve 30 which is secured to ashaft 32 suitably journalled for rotation in the wall of casting 2. Theparticular arrangement of the opening 28 and control valve 39 thereforis not shown in detail as such construction is not material with respectto the invention claimed.

The air which flows through the opening 28 and passage 8 enters achamber 33 in the upper part of the casting 4 which is not divided, asis the lower part of such casting. Positioned in the chamber 33 are twoprimary venturi tubes '34 and 36 which discharge approximately at thethroat of larger venturi tubes 38 and 40, respectively, formed by thewall of casting 4 and in which are the mixing chambers 10 and 12. Themain fuel inlets, which will be later described, supply fuel to theseprimary venturi tubes, in which a relatively rich mixture of fuel andair is formed and such mixture is discharged into the mixing chambers 10and 12 where it is mixed with additional air from the chamber 33,forming a mixture of combustible proportions which is supplied to theengine through the outlet passages 16 and 18.

The position of the choke valve is controlleld automatically in responseto variations in engine suction and temperature by mechanism of the samegeneral construction as that shown in copending application, Serial No.264,136 filed December 29, 1951, of Olson et al. In View of thisdisclosure and because the choke control mechanism forms no part of thepresent invention, the structure of such mechanism is not shown indetail and is only briefly described.

The shaft 32 has secured thereto at the left end, as seen in Fig. 1, anarm 42 having a laterally extending portion 44 which is engaged by thefree end of a coiled bimetallic thermostat 46, the other end of which isconnected to a stud 48 which is fixed in position so that upon changes,

reached, there is substantially closing pressure on the choke valve.

The lower end of arm 42 is pivotally connected to a rod extending from apiston 59 slidable in a cylinder 52 to which the manifold suction orpartial vacuum is communicated. Upon increase in manifold vacuum, thepiston 50 is moved in a direction to open the valve 30 against the 1pressure exerted by the thermostat. l

assapos ,Ihe,. end ofishaft .32 extends into a. supplemental housing 54which is secured in any suitable way to the casting 2, and the chokeoperating mechanism is all positioned within this housing. .A coverplate '56 which may be either metal qrplastic and islgenerally thelatter, as indicated in Fig. l, is secured to the'housing 54 in anysuitableway; as;by screws 58. This plate is adjustable on the housing,to-vary theinitialpressure exerted by the thermostatiQr any, giventemperature. Thisis effected byrotationof therstud tfi which is fixed inthe cover plate and towhichone end, of the thermostat is connected.Heated air is drawn through the passage 61) in the cover plate ,toheatther'thermostatiin the conventionalway.

mechanism so far described forms no part of the inyention claimjedinthis application, which relates entirely tormeans forintroducing fuelinto the venturi tubes 341and3fi and thisrnechanism will now bedescribed.

In this deyice, the float chamber instead of being more or'lessconcentric with reference to the intake passages, as is trueof mostpresent day carburetors. is positioned entirely atone sideof the intakepassages, as shown in Fig. 311. jfiqat. ham i designated y e mera 79 andisa part of ,thecasting A, The valve which controls admission of fuel tothe chamber 79 is of standard conventional constructionand is not shown,but the action of such valyeis controlled by a float 72 in the usual wayto maintain a constant fuel level in the chamber 78. The float ispivqtedon a pin 76 mounted in brackets 77 dependingfromi-the casting 2and the valve which controls fuel flow into chamber 7%) rests on plate78 which is secured to the float and is pivoted on pin 76, so thatupward movement of the float closes the valve when fuel chamber reachesthe proper level. The means for conveying fuel from chamber 70 to thetwo venturi tubes is the sainein construction and Fig. 3 shows the meansfor supplying fuel to tube 36.

means includes a bore 78 in the wall of casting 4 which connects the"chamber '78 with a vertical well 80 also ronaed'n thecastin g The well,at its upper end, connects 'with'a chamber 82 formed in a small casting8 4 which is secured screws'87 to a horizontal surface of thec'asangaaad. the venturi tubes 34 and 36 are formed ir'fthis EastingAlso formed in the casting 84 is a passage '85; one end of whichconnects with the venturi "Edafid'the other eiidfop en s into chamber 33to repeiye aif therefrom. A suitable gasket 88 is positioned between't'hefcas'ting84' and the surface of casting 4 to which it is seciired.'i i The chamber' 82 and the passage 86 are connected by a. bore inwhich is tightly fitted a fuel supply tube 99 which csauue srui from thewell 80 to the passage 86. This tube isfofithef shape shownin Fig. 3, isclosed at its lower end and the end ofzthe tube is bevelled, asindicated at QZQfoIa' purpose which will be set forth later. The tubenew. 1 admittedt the topof the well through a vent passage: 96 indicateddiagrammatically by dotted lines in Fig. 3. As the throttle is'progressively opened, the suction in the venturi tube 36 will increase,the level of fuel in the well will fall and the openings 94 will beprogressively uncovered, permitting air to flow through such openingsinto tube to form an emulsion of fuel and air therein.

Flow of fuel from the chamber 70 into the well 80 is controlled by afuel metering plug 98 screwed into the wall of casting 4 and having acalibrated fuel passage 100 therein.

Positionedwithin the fuel tube 99 is a partition plate 101 whichterminates at the upper end of the tube, as indicated in Fig. 3 and asshown, extends toward the bottom of the tube for approximatelytwo-thirds of the length. of .the tube, but the length of the plate may.be somewhat varied. This plate divides the upper portion of .thertubeinto two' fuel delivery passages of substantially equal cross-sectionalarea and performs a function more fully described later. a

dedwith a series of openings 94 and air is F As already. indicated,. theconstruction. of the fuel well and associated pants cooperating witheach of the venturi tubes is identical, there being two wells 80, twofuel tubes 90 and associated parts of exactly the same construction. Inaddition to the bore 7 8 for supplying fuel to each well 80, each wellhas an auxiliary fuel passage 102 leading to a bore 104 formed in thecasting 4 below chamber 70 at a point about midway between the two endsof chamber 7Q, as seen in Fig. 2. Flow of fuel into this bore from thechamber 70 is controlled by a single valve which is operable in responseto variations in manifold vacuum. A valve housing 106 is positioned inthe bore 104 and has a passage 108 connecting the interior of thehousing with the chamber 70. This passage is controlled by a valve 110positioned in the housing and normally urged toward closing position bya spring 112, also positioned in the housing between a shoulder on thevalve and a closure member 1 14 at the bottomof the :housing to permitfuel toflow from the housinginto passage 70 when the valve t lt) ;isopen.

The .valve is operated by .a rod 118 which is lifted by manifold suctionduring most operation with the throttle only partly. open :so. thatspring 112 will hold the valve 110v closed. However, as. the throttlesmove toward open position, the manifold suction falls and the rodmoves-downwardly, opening the valve 110 and permitting fuel to flow fromthe chamber .70. into housing 106 and through passage 102,'to augmentthe fuel supplied to the well 80 by the main metering passage 100. Thisauxiliary fuel. supply means and control mechanism is of substan tially,the. same construction as shown in the copending application previouslyreferred to.

It will be apparent upon consideration of Fig. 3 that the partitionplate 101 divides the upper end of the fuel delivery tube 90- into twoseparate fuel outlets 120 and 122 which areat different levels, theoutlet 122 being above the outlet 1120. Fuel is caused to flow fromthese outlets by the pressure differential between the atmosphericpressure which is maintained above the fuel in chamber 70 and thesubatmospheric pressure which is maintainedlin the passage 86, and it isobvious that a slightly greater pressure differential is required tocause flow of fuel from the, outlet 120 than is necessary to effect flowfrom the outlet 122.

The. idling fuel supply system is not shown herein because itsconstruction is not material with reference toend qteashu e 0 incr asean b mes sufiicientto cease a flow of-fuel from both outlets, but flowfrom ut et .1 2 ill art before f fr m Outlet 20 w l be initiated.Therefore, as the flow of fuel from the idling fuel system decreasesduring opening of the throttles, flow fromv each main supply tube 90will begin and will increase as the throttles open, but it will increasemore gradually than if the partition plate 101- was not provided,because the outlets 122 and 120 are successively rendered efiective.Therefore, during opening of the throttles, in this particular part ofthe operating range, there is a gradual and smooth increase in fuel flowfrom each main supply tube, whichwould not be effected without thepartition plate. This will result in smoother and more satisfactoryengine operation under the conditions dect d By beyelling the deliveryend of tube 90 as indicated in the drawings, the. aspiratingeifect ofthe air which fiowsthrough passage..86 at relatively high velocity isincreased. and .the elevation ofoutlet 120 with reference tooutlet 122-isinere asedv by comparison with what itwould be if the entire end ofthe tube was flush with the wall of passage 86.

Attention is also called to the fact that the partition 101 would aid ineliminating any difficulties which would be encountered if any largevapor bubbles were formed in the lower part of tube 90. If such bubbleswere formed, and the partition plate not present, these large bubbleswould pass out of tube 90 into passage 86, resulting in appreciableirregularity of fuel flow. If the partition plate is provided, any largebubbles which might be formed are broken up by the plate into muchsmaller bubbles which, although carried on into the passage 86, willcreate much less irregularity in fuel flow than would be effected by thelarger bubbles which might be introduced into passage 86 without theplate 101. Also, the plurality of smaller bubbles would probably notreach passage 86 at exactly the same time, which would also decreaseirregularity of flow.

At the right of Fig. 1 is shown a link 130 the upper end of which ispivotally connected to an arm secured to the choke valve shaft 32. Atits lower end, this link is connected to an idle control mechanism whichis not shown but which, when the temperature is low, causes the throttleto be a little further open at its idling position so that the idlespeed is increased at low temperatures. This mechanism forms no part ofthe invention claimed and need not be fully illustrated or describedherein.

While the embodiment of the present invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. In a carburetor having a mixture passage adapted to supply acombustible mixture of fuel and air to an internal combustion engine, athrottle valve for controlling the quantity of mixture supplied to theengine and an air inlet for admitting air to said mixture passage; meansfor supplying fuel to said mixture passage comprising a fuel supplychamber, a substantially vertical fuel well in communication with andreceiving fuel from said fuel chamber, a fuel delivery tube extendingdownwardly into said well and supplying fuel to said mixture passage,said fuel delivery tube being positioned at an angle to the verticaladjacent its discharge end, a partition plate in said fuel delivery tubedividing said tube into two seperate fuel delivery passages positionedat different levels, a passage with which the discharge end of said fueldelivery tube communicates, the axis of which is substantially normal tothe axis of said tube and having at one end an air inlet, said fueldelivery tube having its discharge end terminating at an acute angle tothe axis of the tube adjacent such discharge end, whereby the tube atone side projects appreciably into said last named passage and at theopposite side terminates substantially flush with the wall of saidpassage.

2. In a carburetor having a mixture passage adapted to supply acombustible mixture of fuel and air to an internal combustion engine, athrottle valve for controlling the quantity of mixture supplied to theengine and an air inlet for admitting air to said mixture passage, meansfor supplying fuel to said mixture passage comprising a fuel supplychamber, a fuel well in communication therewith and receiving fueltherefrom, a fuel supply passage connecting with the mixture passage sothat air is drawn through said supply passage at a. speed proportionalto the flow of air through the mixture passage, a fuel delivery tubepositioned in said well and delivering fuel to said fuel supply passage,and a partition plate in the outlet end of said tube and extendinglongitudinally with respect thereto, said tube having a beveled edgeprojecting within said supply passage, said partition plate terminatingat one end in the beveled end of said tube so as to divide said tubeinto two separate fuel delivery passages, one of which is upstream ofthe other relative to the air flowing through the fuel supply passage,said beveled edge increasing in length in the upstream direction so thatair flowing through the fuel supply passage will cause fuel to flowfirst through the upstream fuel delivery passage.

3. In a carburetor as set forth in claim 2 in which said tube is closedat its lower end and has fuel inlet ports in the side wall thereof, andfurther in which said partition plate extends downwardly in said tubethrough the major part of its length but terminates an appreciabledistance from the closed lower end of the tube.

4. In a carburetor having a mixture passage adapted to supply acombustible mixture of fuel and air to an internal combustion engine, athrottle valve for controlling the quantity of mixture supplied to theengine and an air inlet for admitting air to said mixture passage, meansfor supplying fuel to said mixture passage comprising a fuel supplychamber, a fuel well in communication therewith and receiving fueltherefrom, the axis of said fuel well being substantially parallel tothe axis of the mixture passage, a fuel supply passage connecting at anoblique angle with the mixture passage so that air is drawn through saidsupply passage at a speed proportional to the flow of air through themixture passage, a fuel delivery tube positioned in said well anddelivering fuel to said fuel supply and partition plate in the outletend of said tube and extending longitudinally with respect thereto, saidtube having a beveled edge projecting within said supply passage, saidpartition plate terminating at one end in the beveled end of said tubeso as to divide said tube into two separate fuel delivery passages, oneof which is upstream of the other relative to the air flowing throughthe fuel supply passage, said beveled edge increasing in length in theupstream direction so that air flowing through the fuel supply passagewill cause fuel to flow first through the upstream fuel deliverypassage.

References Cited in the file of this patent UNITED STATES PATENTS1,935,350 Chandler Nov. 14, 1933 2,114,970 Rullison et al Apr. 19, 19382,215,683 Wirth Sept. 24, 1940 2,635,861 Olson Apr. 21, 1953

